Custom build not displaying

I upgraded my custom build’s motherboard to a prime Z790-V AX. And my cpu to an i9 12900K. The thing powers on the fans and rgb but nothing displays. I’ve tried to take out the gpu (GTX 1080) and plug an hdmi into the motherboard but that still doesn’t work. I’ve tried different monitors and nothing seems to work. Any advice? I’m going crazy trying to figure it out